The present invention relates to a voltage regulator for an alternator, and in particular to a regulator of the monofunction type for a nine-diode alternator which may be used in automotive applications.
It is known that in regulation systems of the monofunction type, the exciter winding of the alternator and the voltage regulator which drives it are supplied by the stator windings of the alternator via an auxiliary trio of diodes and that a breakdown warning lamp is inserted between the trio of diodes and the main switch (ignition key of the vehicle).
The current art provides for the construction of the regulator as an integrated circuit with the exception of its actuator stage which is of discrete components.
This stage comprises a pair of transistors in the Darlington configuration, rather than an individual transistor, to provide a high current gain, and is disposed in series with the exciter winding of the alternator. At the time of starting, the alternator does not supply current and the exciter winding and the regulator are supplied with current by the battery via the lamp. In this case, the voltage drop of the Darlington pair of the actuator stage must be sufficiently low to provide the excitation current required for the starting of the alternator at a low rotational speed.
The voltage drop in an integrated Darlington pair is usually greater, for technical reasons, than in a discrete Darlington pair which makes starting of the alternator critical. This leads to the need to integrate the actuator stage together with the other parts of the regulator.